The U.N. children's fund UNICEF says Syria's civil war killed 1,600 people last week, making it the deadliest seven-day period of the 18-month conflict.

UNICEF spokesman Patrick McCormick said Sunday the death toll included some children, but he did not elaborate or say how he obtained the figure.

Syrian opposition activists have been reporting daily death tolls of 100 to 200 people in the past week as President Bashar al-Assad's forces intensified the use of air power to crush the uprising against his autocratic rule. Daily casualty reports from rebel and government sources are difficult to verify because the fighting and government censorship have kept many foreign journalists away.

In the latest unrest on Sunday, Syrian state media said two bombs exploded near a security compound in Damascus, wounding four people in an attack claimed by Free Syrian Army rebels.

The state news reports denounced the bombings in the Abu Rummaneh district of the capital as an act of terrorism.

In another attack, the Syrian government said a car bomb exploded in a Damascus suburb late Saturday, killing 15 people. The Syrian capital and its suburbs have seen a series of bombings in recent months, mostly targeting the security establishment of President Assad.

Syrian opposition activists said Mr. Assad's forces bombarded rebel-held areas of several provinces on Sunday. Syria's uprising began in March 2011 with peaceful protests but escalated into a civil war as he tried to suppress opponents with deadly force.

New international peace envoy Lakhdar Brahimi said Saturday change in Syria is “necessary, indispensable and unavoidable.” But in an interview with Arab television network Al Jazeera, he also said it is “too early to speak about who should go and who should stay.” Western powers and their Arab allies have demanded that Mr. Assad step down, but Russia, China and Iran have rejected such calls as interference in Syrian affairs.

Brahimi, a former Algerian diplomat, assumed the post of U.N.-Arab League envoy on Saturday, after his predecessor Kofi Annan quit in frustration as Syria's fighting escalated.

The new envoy said he will speak to Mr. Assad to try to resolve the conflict and insisted such a move “is not a step backwards.” Before resigning, Mr. Annan said the Syrian president “must leave office.”

Several Syrian rights groups said the conflict's death toll for August was at least 4,900.